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Chapter 2

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York University
BIOL 1000
Tamara Kelly

BIO 1000 Notes Chapter 2.1 Notes: Cell Theory(Notion of common descent) Ex: Kids from fertilized egg(common descent = egg) • All organisms are composed of one or more cells. • The cell is the basic structure and functional unit of all living organisms • Cells arise only from the division of pre-existing cells. • Bacteria, archaea, some protists(amoebas), some fungi(yeast) = UNICELLULAR(each cell functionally independent organisms) • Plants & animals = complex MULTICELLULAR(If cells broken= cant reproduce, grow) • All forms of life grouped into 3 domains = Bacteria, the Archaea, the Eukarya. NOTE: bacteria & archaea originally grouped into single domain: Prokaryota(prokaryotes) • Smallest bacteria have diameter of 0.5 µm(micrometer). Chicken yolk = 1cm(0.1m) HumaEye Plasma Membrane: Bilayer made of lipids with embedded protein molecules(cells bounded by this). Function = Separate/protect content of cell from external environment. TRANSPORT materials into & out of cell. Phospholipid Bilayer: Hydrophobic(non-polar/can’t mix with water) barrier to the passage of water-soluble substances. BUT selected water-soluble substances can penetrate cell membrane through transport protein channels. Arrangement = phospholipids two molec thick • Selective movement of ions & water-soluble molecules through TP maintain ionic & mol enviro • DNA contains hereditary info(which is organized in the form of genes-segments of DNA that code for individual proteins. • Phospholipid molecule = Hydrophilic Head(phosphate) & two fatty acid hydrophobic tails. Cytoplasm: Contains the organelles the cytosol & cytoskeleton. (Interior of cell) • All parts of cell between plasma membrane & central region MAKE UP IT • Vital cell activities occur here = synthesis & assembly of molec required for growth & repro(except those made in central region) & conversion of chemical & light energy into forms that can be used by cells. • ALSO conducts stimulatory signals from outside into cell interior Organelles: Small organized structures important for cell function. Cytosol: Aqueous(water) solution containing ions & various organic molecules. Cytoskeleton: Protein-base framework of filamentous structures help maintain proper cell shape & plays key roles in cell division & chromosome segregation from cell-generation to next • ONCE thought to be specific to eukaryotes. Prokaryotes have it too. BIO 1000 Notes • Prokaryotic ones = create & maintain proper shape of cells in cell division & for certain bacteria, determining polarity of cells. Two Types of Cells: • Prokaryotic & eukaryotic. Prokaryote not used anymore as bacteria & archaea are evolutionarily distinct. • Prokaryotic still used = refers to particular cell architecture, ONE LACKING A NUCLEUS Nucleoid: DNA-containing central region of the cell (Has no boundary membrane seperating it from cytoplasm. <
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